The present invention relates to a process of developing a high resolution image on a surface of a magnetic member with a dry magnetic toner with removal of excess toner on the magnetic member followed by transfer of the toner to a substrate preferably using heat and pressure. The present invention is particularly adapted to the formation of a high resolution image which serves as a resist in the manufacture of printed circuit boards.
Turney U.S. Pat. No. 3,514,803, Krause U.S. Pat. No. 3,741,157, Hudson U.S. Pat. No. 4,014,065, Stack U.S. Pat. No. 4,260,235 and Edwards et al. U.S. Pat. No. 4,233,382 discloses various techniques and structural designs in selectively removing unwanted powder material from a substrate. U.S. Pat. No. 3,514,803 discloses apparatus using opposed elongated vacuum nozzles, one nozzle to lift free powder with a second nozzle to resist lifting of a sheet substrate. U.S. Pat. No. 3,741,157 discloses use of a nozzle with a plurality of jets of air directed onto a surface with vacuum means to carry away dislodged material. U.S. Pat. No. 4,014,065 discloses a system for removing unwanted particles containing a magnetic developer material. The removal means contains a chamber having entrance and exit ports with the cross section of the entrance to exit port being sufficiently small to assure substantially uniform air flow across the entrance port when the chamber is subjected to negative pressure through the exit port. The patent discloses that the developed surface of the circular member is subjected to substantially uniform shearing air flow and the suction device contains an arcuate terminal portion which extends along the cylindrical member containing the latent magnetic image. U.S. Pat. No. 4,260,235 discloses a magnetic developer removal system to remove excess developer material from a circular member having a latent magnetic image developed with vacuum scavenging chamber whereby the leading edge of the scavenging chamber is given a curved shape to aid in creating a venturi and a trailing edge shaped as knife edge. U.S. Pat. No. 4,233,382 discloses a process for reproducing graphic information by forming a magnetic image in a premagnetized layer of chromium dioxide with heating of the chromium dioxide to above its Curie point in selected areas. Uncharged ferromagnetic toner particles are applied uniformly to the chromium dioxide layer but adhere only to the magnetized areas. Excess toner particles are removed by a vacuum knife. The toner particles are electrostatically transferred to a substrate.
Nacci et al. U.S. Pat. No. 4,338,391 discloses a process of forming an image of toner on a latent magnetic image in a magnetic member followed by direct transfer to a surface with coalescence of the toner. Excess background toner is removed from nonmagnetized background areas of the magnetic member by means of a vacuum knife, air knife or combination thereof. The surface which is not protected by the transferred toner is then permanently modified by etching or plating.
The present invention is an improvement over the process disclosed in Nacci U.S. Pat. No. 4,338,391 in the step of removing background toner from a image magnetic toner on a magnetic member followed by transfer of the magnetic toner image to a substrate.